Magnetic disks and disk drives are conventionally employed for storing data in magnetizable form. Preferably, one or more disks are rotated on a central axis in combination with data transducing heads positioned in close proximity to the recording surfaces of the disks and moved generally radially with respect thereto. Magnetic disks are usually housed in a magnetic disk unit in a stationary state with a magnetic head having a specific load elastically in contact with and pressed against the surface of the disk.
The increasing demands for higher areal recording density impose increasingly greater demands on flying the head lower because the output voltage of a disk drive (or the readback signal of a reader head in disk drive) is proportional to 1/exp(HMS), where HMS is the space between the head and the media. Therefore, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated transducer head, thereby permitting the head and the disk to be positioned in closer proximity with an attendant increase in predictability and consistent behavior of the air bearing supporting the head.
The formation of each of the layers of the recording medium is based in part on the surface conditions of the previous layer. Thus, it is important that the non-magnetic substrates meet a strict set of requirements so that the subsequent layers formed thereon may be properly arranged. For example, if the overall surface of the substrate has an undesirable curvature, the head will not always be appropriately spaced from the media. Thus, the substrate must have an overall flatness. On a smaller scale, the waviness of the surface of the substrate must also meet specific requirements. If there are significant scratches or bumps in the surface, those scratches and bumps may show up in the subsequent layers. On an even smaller scale, the roughness of the surface on the scale of Angstroms must also be very low. If the roughness is too high, the head will not be able to glide smoothly over the media. As a result, the recording media will be defective. Therefore, it is very important that the surface of the substrate meet strict requirements with respect to smoothness.
In order to smooth the surface of the substrates, they are first ground to a desired width, flatness and waviness using grind stones. In many applications both sides of the substrates are utilized for recording media. Once the substrates are ground to meet these requirements they are further processed to meet small scale smoothness requirements. The small scale roughness is usually controlled by a polishing process after grinding.
There is, however, a need for a dresser which will dress grind stones such that they operate at a high removal rate and produce substrates with good mechanical surface characteristics.